Mac OS X is a good thing, but as with all good things, it does come with a price. You must have a modern Mac to be able to use it. Apple states that you must have a Power Mac G5, Power Mac G4, Power Mac G3 (Blue & White), iMac, eMac, PowerBook G4, PowerBook G3 (with built-in USB), or an iBook to be able to run it. You also must have at least 128MB of RAM to run it (but I think you will have a better experience if you have at least 256MB). Also, your Mac needs to have a built-in display or one that is connected to an Apple-supplied video card. Finally, you need at least 2GB of disk space (but if you want to take advantage of Mac OS X's organization and security scheme, you should have a lot more free space than that).
For help moving to Mac OS X version 10.3 from previous Mac OS X versions or from Mac OS 9 or earlier, see Appendix A, "Installing and Maintaining Mac OS X," p. 947.
Apple does not support Mac OS X running on early hardware, although you might be able to get it to run on an older machine. You might also be able to get Mac OS X to run on a machine that has an upgrade card installed in it; however, support for specific upgrade cards is a hit-or-miss proposition.
As with any tool as sophisticated and powerful as Mac OS X, it can take some time to learn how to use it effectively. This learning curve can also be considered one of Mac OS X's costs. This cost is one that this book can lower for you. As you read through the rest of this book, you will quickly become comfortable with all aspects of Mac OS X. And as you explore more of the OS, you can always come back to specific parts of the book to guide you on your way.